فهرست مطالب

Advanced Structural Engineering - Volume:13 Issue: 3, Autumn 2023

International Journal of Advanced Structural Engineering
Volume:13 Issue: 3, Autumn 2023

  • تاریخ انتشار: 1402/11/23
  • تعداد عناوین: 4
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  • Vibration-based cable tension estimation using two iterative algorithms: Methodology and experimental validation
    Latif Doosti, Omid Bahar, Mohsen Ghafory-Ashtiany, Mohsen Elmi Page 0

    In this paper, a reliable method based on two iterative algorithms is proposed for the estimation of cable tension forces. In this method, a Finite Element model, considering the cable's geometric and mechanical characteristics, is used in order to obtain mass and stiffness matrices. The initial geometric stiffness matrix of the structure is calculated according to the taut string theory, assuming an initial value for the tension force. Furthermore, the natural frequency of the MDOF system is calculated using Ritz Method, and then compared to measured vibration frequencies, which can be obtained by output-only system identification methods. In this method, the difference between the computational and measured frequencies should not exceed the pre-defined threshold, otherwise the iteration process would be repeated after modifying the initial assumption of the cable force. To evaluate the accuracy and the effectiveness of the proposed method, an experimental study was performed on an external cable in the IIEES structural laboratory. Also, existing cable forces of the Hwamyeong cable-stayed bridge in South Korea have been employed. In both cases, the iterative method is compared with common theoretical and empirical equations in the literature. The results have shown that the iterative method is of high accuracy and great applicability, reducing the difference to even less than 2%.

    Keywords: System Identification, Post-Tensioning, Cable Structures, Tension Estimation, Vibration-Based Methods
  • Cold rolling techniques in mechanical splices: Experimental investigations
    Mohamad Reza Shokrzadeh, Fariborz Nateghi Allahe, Taleb Sadeghian Page 0

    This study presents a comprehensive evaluation of the performance of oversize threaded splices under cyclic loading conditions. The research includes monotonic tensile testing and cyclic loading experiments to investigate the seismic behavior of the splices. The experimental results demonstrate that the splices exhibit lower values of εu (strain at peak load) in cyclic loading compared to monotonic tensile testing. This suggests that the cyclic response can serve as a conservative lower bound for the mechanical performance of the splices. The findings highlight the importance of considering cyclic loading conditions when determining conservative lower bounds for the design and evaluation of threaded splices. Understanding the behavior and performance of threaded splices under cyclic loading is crucial for ensuring their reliable and safe operation in seismic regions.

    Keywords: Mechanical Threaded Splice, Ductile Members, Cold Rolling, Modifying Threaded
  • Investigating the effect of increasing the height of bridge piers on seismic behavior of isolation systems in urban bridges (A case study on the Hesarak Bridge)
    Mehdi Firoozbakht *, Aliakbar Edalati Page 1

    Bridges are vital to modern transportation infrastructure, providing convenient and efficient access to different locations. Because of their structural simplicity and low degree of indeterminacy, bridges tend to be particularly vulnerable to damage and even collapse when subjected to earthquakes. The costs of their construction and retrofitting are high, so the maintenance of these capitals is one of the necessities of urban management. This paper investigates the influence of increasing the height of bridge piers on seismic behavior of isolation systems in urban reinforce concrete (RC) bridge. For this purpose, the seismic performance of the Hesarak Bridge constructed in Karaj city, Iran with two isolation systems; i.e. the existing elastomeric rubber bearing (ERB) and a proposed lead rubber bearing (LRB) are discussed by changing three times the height the bridge piers as compared with the existing situation. The numerical model was implemented in the well-known FEM software CSiBridge. The isolated bridge has been analyzed using nonlinear time history analysis (NTHA) method with seven pairs of earthquake records and the results are compared for the two isolation systems in both height modes. The results showed that with the increase in the height of the bridge piers, the natural period of the LRB isolated system changes from 2.7 to 2.77 seconds and on the other hand, this value increases from 1.37 to 1.62 in the ERB isolated system. The ratio of maximum base shear force for the bridge with the LRB to the ERB isolators under given ground motions ...

    Keywords: Bridge, Keywords: RC, ERB, LRB, NTHA
  • Saeed Baharipour, Mahdi Nani *, Mojtaba Hosseini, Abdolreza Sarvghad Moghadam, Mehran Mehran S. Razzaghi Page 2

    Due to the importance of seismicity in the region of Iran, the improvement and retrofitting of structures has always been the focus of competent employers and engineers. In order to achieve the goals of this research, a three-story concrete school structure in need of improvement has been selected. Then, the investigation of possible improvement options (three improvement options: 1 with braces, 2 with friction damper, 3 using FRP in the columns) has been done in Opensees software. In the following, incremental nonlinear dynamic modeling and analysis under selected earthquake records using the recommended FEMA P695 accelerometers for co-based seismic records (5 acceleration maps for the far field and 5 acceleration maps for the near field) has been performed. Then a comparison between the fragility curves for different states has been made. In this research, the behavior of the building against different earthquake intensities is shown According to the results obtained from other non-linear analyses, it can be seen that the maximum capacity obtained is in good agreement with the results of these analyzes and this method is very suitable for evaluating the behavior of buildings and ultimate capacities against earthquakes. Also, it can be a good alternative method for approximate methods such as pushover analysis to determine the performance level of the building and to determine the behavior of the building.

    Keywords: Fragility Curves, Concrete Structure, Seismic Rehabilitation, FRP Strips, Frication Dampers